Case Report: Pancreatic Paraganglioma Mimicking a Well-Differentiated Neuroendocrine Tumor: The Importance of Cytokeratin Immunohistochemistry.

Paragangliomas (PGLs) are uncommon neuroendocrine tumors most commonly found in the head and neck that originate from neural crest cells. Primary pancreatic paraganglioma is exceedingly rare and has largely been described in case reports and small case series. We present the case of a 79-year-old woman with an incidental pancreatic head lesion initially favored to represent a well-differentiated neuroendocrine tumor. Endoscopic ultrasound with rapid on-site cytopathologic evaluation demonstrated neoplastic cells with neuroendocrine features. Further immunohistochemical (IHC) workup demonstrated tumor cells negative for cytokeratins and positive for GATA-3, supporting a diagnosis of paraganglioma over a well-differentiated neuroendocrine tumor. Cytokeratin immunohistochemistry should be employed alongside neuroendocrine markers in the workup of neuroendocrine tumors to avoid misdiagnosis.